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International Study on Age-related disparity in Cancer patient survival

Periodic Reporting for period 1 - ISAC (International Study on Age-related disparity in Cancer patient survival)

Reporting period: 2019-07-22 to 2020-07-21

Cancer patients are increasingly surviving their disease, but disparities in cancer outcomes still persist, and even widen, for some groups of patients. This is the case for older adults as they have not benefitted from the improvements in cancer diagnosis and treatment at the same magnitude as their middle-aged counterparts. Older adults account for the largest proportion of cancer diagnoses, and with the number of diagnoses expected to double in two decades, such disparities will result in a substantial amount of years of life lost due to unfair age-related disparities in cancer survival. The ISAC project thus aims to investigate the role of comorbidities and other factors in cancer survival disparities among older patients compared with younger patients, which will aid interventions to increase the probability of survival regardless of age.
Specifically, the project aims at:
1 - Determining the contribution of comorbidities, treatment and stage at diagnosis on age-related disparities in colon and lung cancer survival in New Zealand and England;
2 - Determining the effect of social determinants notably socioeconomic position and ethnicity on age-related disparities in colon and lung cancer survival in New Zealand and England;
3 - Assessing the impact of eliminating age inequalities on colon and lung cancer survival to help inform health policymakers in England ).
During the outgoing phase of the global fellowship in New Zealand, the fellow reviewed the literature review on factors influencing age disparities in colon and lung cancer survival, taking colon and lung cancers, as exemplars. This review aimed to identify patterns of age-related differences based on patient and clinical characteristics and the potential gaps in knowledge to inform future research. Results showed that although age is one of the most important prognostic factors in cancer survival, age disparities in colon and lung cancer survival have so far been understudied in population-based research. Moreover, regardless of the cancer site, the included studies were highly heterogeneous and often of poor quality. The magnitude of age disparities in survival varied greatly by sex, ethnicity, socio-economic status, stage at diagnosis, cancer site and morphology, the number of nodes examined, and by treatment strategy. Although results were inconsistent for most characteristics, we consistently observed greater age disparities for females with lung cancer compared to males. Also, age disparities increased with more advanced disease for colon cancer and decreased with more advanced disease for lung cancer. This review justified the need for further studies to better understand age disparities in colon and lung cancer survival.

In a second work, the fellow described the role of patient-related and clinical factors on age disparities in colon cancer survival among patients aged 50-99 years at diagnosis using New Zealand population-based cancer registry data linked to hospitalization data. Specifically, the fellow described the role of sex, ethnicity, socio-economic deprivation, emergency presentation, stage at diagnosis and comorbidity on the age difference in colon cancer survival. This work confirmed that survival decreased as the age at diagnosis increased, notably in advanced disease and missing stage. It showed that the excess mortality in older patients was minimal for localised cancers, maximal during the first six months for regional cancers, the first 18 months for distant cancers, and over the three years for missing stages. The age pattern of the excess mortality hazard varied according to sex for distant cancers, the route to diagnosis for regional and distant cancers, and comorbidity for cancer with missing stages. Overall, the results showed that factors reflecting timeliness of cancer diagnosis affected the most the difference in survival between middle-aged and older patients, probably by impacting treatment strategy. Because of the high risk of poor outcomes related to treatment in older patients, efforts made to improve earlier diagnosis in older patients are likely to help reduce age disparities in colon cancer survival in New Zealand.

The fellow started a similar analysis using lung cancer data.
For the first time, the ISAC project offers a comprehensive description of age disparities in survival for colon and lung cancers, two common cancers in older patients, with the ultimate goal to reduce the survival gap between older and younger patients.